Tutorial by Examples: e

The when is a keyword added in C# 6, and it is used for exception filtering. Before the introduction of the when keyword, you could have had one catch clause for each type of exception; with the addition of the keyword, a more fine-grained control is now possible. A when expression is attached to ...

The isEqual: method is the only reliable way to determine whether two images contain the same image data. The image objects you create may be different from each other, even when you initialize them with the same cached image data. The only way to determine their equality is to use the isEqual...

Directives, as the name suggests, are direction or instructions for the container to follow when translating a JSP to a servlet. There are 3 directives namely page, include and taglib which you can use in your JSP. Below is a simple example of using page directive: <%@ page isErrorPage="tr...

Send an HTTP response with status code 200 to indicate a successful request. The HTTP response status line is then: HTTP/1.1 200 OK The status text OK is only informative. The response body (message payload) should contain a representation of the requested resource. If there is no representation...

NOTE: In most cases, it is better to use a UIButton instead of making a UILabel you can tap on. Only use this example, if you are sure, that you don't want to use a UIButton for some reason. Create label Enable user interaction Add UITapGestureRecognizer The key to create a clickable UIL...

Assuming that you have successfully created a JFrame and that Swing has been imported... You can import Swing entirely import javax.Swing.*; or You can import the Swing Components/Frame that you intend to use import javax.Swing.Jframe; import javax.Swing.JButton; Now down to adding the J...

Leaflet is an open-source JavaScript library for making dynamic maps for the web. RStudio wrote R bindings for Leaflet, available through its leaflet package, built with htmlwidgets. Leaflet maps integrate well with the RMarkdown and Shiny ecosystems. The interface is piped, using a leaflet() funct...

PHP is a loosely typed language. This means that, by default, it doesn't require operands in an expression to be of the same (or compatible) types. For example, you can append a number to a string and expect it to work. var_dump ("This is example number " . 1); The output will be: ...

When reading from a file, we want to be able to know when we've reached the end of that file. Knowing that fgets() returns false at the end of the file, we might use this as the condition for a loop. However, if the data returned from the last read happens to be something that evaluates as boolean f...

Switch statements use non-strict comparison to determine matches. This can lead to some nasty surprises. For example, consider the following statement: switch ($name) { case 'input 1': $mode = 'output_1'; break; case 'input 2': $mode = 'output_2'; bre...

When you install Oracle 11g or 12cR1, an older version of Apex is pre-installed. It is highly recommended to upgrade it to the latest version. Go to apex.oracle.com and download the latest version of Apex. Follow the documentation for the specific version to install it. Important Docu...

Add the following dependency to the build.gradle file: compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.5' Add the following permissions to the AndroidManifest.xml file: <uses-permission android:name="android.permission.INTERNET" /> <uses-permiss...

Load an image, decode it into a bitmap, and display the bitmap in an ImageView (or any other view which implements the ImageAware interface): ImageLoader.getInstance().displayImage(imageUri, imageView); Load an image, decode it into a bitmap, and return the bitmap to a callback: ImageLo...

A very useful and logical follow-up to histograms would be to plot the smoothed density function of a random variable. A basic plot produced by the command plot(density(rnorm(100)),main="Normal density",xlab="x") would look like You can overlay a histogram and a density...

To change MySQL's root user password: Step 1: Stop the MySQL server. in Ubuntu or Debian: sudo /etc/init.d/mysql stop in CentOS, Fedora or Red Hat Enterprise Linux: sudo /etc/init.d/mysqld stop Step 2: Start the MySQL server without the privilege system. sudo mysqld_safe --skip-grant-tab...

Haskell has list comprehensions, which are a lot like set comprehensions in math and similar implementations in imperative languages such as Python and JavaScript. At their most basic, list comprehensions take the following form. [ x | x <- someList ] For example [ x | x <- [1..4] ] -...

A 'tab bar' is commonly found in most iOS apps and is used to present distinct views in each tab. To create a tab bar controller using the interface builder, drag a tab bar Controller from the Object Library into the canvas. By default a tab bar controller comes with two views. To add additional...

Using the Story Board: Select the tab bar item from the corresponding view controller and go to the attributes inspector If you want a built-in icon and title, set the 'System Item' to the corresponding value. For a custom icon, add the required images to the assets folder and set the 'System It...

If you need an ActiveRecord method to raise an exception instead of a false value in case of failure, you can add ! to them. This is very important. As some exceptions/failures are hard to catch if you don't use ! on them. I recommended doing this in your development cycle to write all your ActiveRe...

If you need to delete a lot of records quickly, ActiveRecord gives .delete_all method. to be called directly on a model, to delete all records in that table, or a collection. Beware though, as .delete_all does not instantiate any object hence does not provide any callback (before_* and after_destroy...